Don't think this is version dependent. Actually lcd backlight is controlled by 5v power on lcd connector. Also I never heard this happens normally it might be that the 5v converter from main power->5v is not working and only when you get power via usb you have 5v. Would only make sense for 3.3v boards that also have 3.3v converter for cpu or cpu would stop as well without 5v power. Some boards also have a switch to select that some parts are only powered by usb or by main power->converter.
